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NATO said Haji Mali Khan was seized Tuesday during an operation in eastern Paktia province's Jani Khel district, which borders Pakistan. It was the most significant capture of a Haqqani leader in Afghanistan, and could dent the group's ability to operate along the porous border with Pakistan's lawless tribal areas.

Shortly after NATO's announcement, Taliban spokesman Zabiullah Mujahid denied in a message to Afghan media that Khan had been arrested but provided no evidence that he was free.

NATO described Khan as an uncle of Siraj and Badruddin Haqqani, two of the son's of the network's aging leader Jalaludin Haqqani. However, in a recent report on the Haqqani's by the Institute for the Study of War, Khan appears as a brother in-law to Jalaludin Haqqani.

The Pakistan-based Haqqani network is affiliated with both the Taliban and al-Qaida and has been described as the top security threat in Afghanistan. The group has been blamed for hundreds of attacks, including a 20-hour siege of the U.S. Embassy and NATO headquarters last month.

Last week, U.S. officials accused Pakistan's spy agency of assisting the Haqqanis in attacks on Western targets in Afghanistan - the most serious allegation yet of Pakistani duplicity in the 10-year war.

The United States and other members of the international community have in the past blamed Pakistan for allowing the Taliban, and the Haqqanis in particular, to retain safe havens in the country's tribal areas along the Afghan border - particularly in North Waziristan.

"He was one of the highest ranking members of the Haqqani network and a revered elder of the Haqqani clan," NATO said of Khan, adding that he "worked directly under Siraj Haqqani, and managed bases and had oversight of operations in both Afghanistan and Pakistan.

Khan also moved forces from Pakistan to Afghanistan to conduct terrorist activity, NATO said. "Jalaluddin Haqqani consistently placed Mali Khan in positions of high importance."

NATO also said that Khan had in the past year established a militant camp in Paktia and "coordinated the transfer of money for insurgents operations, and facilitated the acquisition of supplies."

During the operation Tuesday, Khan surrendered without resistance and NATO forces also arrested his deputy and bodyguard, along with a number of other insurgents, the alliance said.

"The Haqqani network and its safe havens remain a top priority for Afghan and coalition forces," NATO concluded.

The NATO statement said security forces have conducted more than 500 operations so far in 2011 in an effort to disrupt the Haqqani network leadership, resulting in the deaths of 20 operatives and the capture of nearly 300 insurgent leaders and 1,300 suspected Haqqani insurgents.